Porting the Edelbrock Pro Flow XT 7137

ASE Doc

Well-Known Member
I'm starting this thread here to talk about the Pro Flow XT for small block chevy. I plan on installing it on a 355 next summer. I chose the XT because of all the performance EFI intake options on the market today, I think the XT shows the most overall potential for combining top end power and midrange torque. While the overall design of the XT is good, the weakness I see is the small runner exits. Mounting it on cyl heads that are port matched to a felpro 1205 gasket(2.09 x 1.28) will leave alot of material inside the gasket openings all the way around each intake port. This could be a pretty big choke point on heads that flow well. My heads are ported Trickflow twisted wedge G2s that flow 270cfm.

I spoke with Eddy tech just to get their thoughts on it. The guy told me that the small runner exit is intended to increase velocity in the flow range of a street driven engine. That makes since except that if the head's intake port is considerably larger than the runner exit, that velocity is going to drop off hard right where it needs to be strongest for fuel atomization. When I brought up extrude honing to smooth the interior casting, I was also told that the rough casting is there to encourage swirl and tumble of the air through the runners. Now maybe I have learned this wrong over the decades that I've done this stuff but I've become pretty sure that the tumble and swirl needs to take place starting at the back of the intake valve and into the chamber. Swirl and tumble in the runners sounds alot like flow killing turbulence.

At any rate, I still plan to work this unit over before it goes on. After pricing extrude honing, I'm thinking of going with my other option of having the top of the plenum cut off and hand finishing the runners and runner entries, surfacing the plenum. I may even add a small amount of volume to the plenum when it goes back together. It appears that the piece was designed primarily for street use for stock or slightly larger ports. To support my heads and cam and make my power goal of 460hp at about 6,300, I think it will need to flow a little more, even at the cost of a slight bit of throttle response and low end torque. My 3,500 stall converter and gears will help cover the low end side anyway.

BTW, I'm here to air my ideas as a long time pro mechanic/ hobbiest engine builder. I hope to start a discussion and welcome any and all opinions and feedback on this intake manifold and my ideas for it.

Sorry, tried to attach some photos of the piece for those unfamiliar with it. Seems my photos are too large.

Again, this is the Edelbrock Pro Flow XT EFI tunnel ram P/N 7137.
 
I know that folks will want the details of the build. It is a 10.2:1 355 with 6" connecting rods. The heads are trickflow twisted wedge G2 with 190 as cast ports, ported to 195. They flowed 257 as cast and now flow 270 @.600. The cam is the TPIS ZZX 240/240 @ .050 (292/292) .560/.560 lift with my 1.5 rockers. 112 LSA, 108 ICL, IC @ 74 degrees ABDC. The spring package is set up for 6,500. The car is a 3,400lb 87 Camaro. 700R4 and 3.23 rear gears.
 
a great deal of the info you may want can be calculated after carefully measuring the intake port and runner length and cross sectional areas.(remember its not the intake port gasket cross sectional opening, cross sectional area, its the smallest part of the port cross sectional area and valve throat areas that limit port flow rates)
if as an example we selected a port with about a 2 sq inch cross sectional area, you'll find max torque on a 350 will fall near 4000-rpm and port stall near 6000-rpm thus it makes sense to match the cam timing and lift/duration and the drive train gearing to match the rpm range,power curve and port flow.
or put a bit differently, theres no sense in selecting a cam designed to operate well at 7600 rpm if you port stalls at 6300 rpm


rtyu1.jpg

rtyu2.jpg

http://users.erols.com/srweiss/calccsa.htm

http://users.erols.com/srweiss/calcplv.htm

http://users.erols.com/srweiss/calchpaf.htm


http://www.wallaceracing.com/chokepoint.php

http://www.rbracing-rsr.com/runnertorquecalc.html
13cal.jpg

17903.jpg

ticalcx1.jpg

http://www.walmart.com/ip/Texas-Instruments-TI-30X-IIS-Scientific-Calculator/1535939
http://www.summitracing.com/parts/cca-5605/overview/
related info, that you might need

http://garage.grumpysperformance.co...heads-for-small-block-chevys.3293/#post-26213

http://garage.grumpysperformance.com/index.php?threads/what-are-these-heads.4702/#post-12742


http://garage.grumpysperformance.co...-by-step-guide-with-pictures.5378/#post-71848

http://noel.prodigitalsoftware.com/NCtpi.html

http://garage.grumpysperformance.co...ther-efi-intake-manifold-info.431/#post-26322

http://garage.grumpysperformance.com/index.php?threads/porting-can-help.462/page-3#post-59145

http://garage.grumpysperformance.co...ads-tuned-intake-turbulence.12998/#post-67611

Volume (CCs) of Head Gasket

CCs of Head Gasket = Bore x Bore x 12.87 x Thickness of Head Gasket
COMMON SBC INTAKE PORTS
felpro # 1204=Port Size: 1.23" x 1.99"=2.448 sq inches

felpro # 1205=Port Size: 1.28" x 2.09"=2.67 sq inches

felpro # 1206=Port Size: 1.34" x 2.21"=2.96 sq inches

felpro # 1207=Port Size: 1.38" x 2.28"=3.146 sq inches

felpro # 1209=Port Size: 1.38" x 2.38"=3.28 sq inches

felpro # 1255 VORTEC=Port Size: 1.08" x 2.16"-2.33 sq inches

felpro # 1263=Port Size: 1.31" x 2.02"=2.65 sq inches

felpro # 1266=Port Size: 1.34" x 2.21"=2.96 sq inches

felpro # 1284 LT1=Port Size: 1.25 x 2.04''=2.55 sq inches

felpro # 1289 FASTBURN=Port Size: 1.30" x 2.31" 3.00 sq inches

http://users.erols.com/srweiss/calccsa.htm

Your RPM computed from your Cross Sectional Area of 1.95
(the smaller AFR HEADS)
and Bore of 4.03 and Stroke of 3.75 is 5,569.12 .

Your RPM computed from your Cross Sectional Area of 2.05
(the Larger AFR HEADS)

and Bore of 4.03 and Stroke of 3.75 is 5,854.72 .
you,ll barely notice the about 300 rpm shift in the power band on the lower part of rpm range but appreciate it much more on the upper edge of that power curve


heres a chart FROM THE BOOK,HOW TO BUILD BIG-INCH CHEVY SMALL BLOCKS with some common cross sectional port sizes
(measured at the smallest part of the ports)

HeadsVsPortFlow.JPG


USE THE CALCULATORS

http://www.rbracing-rsr.com/runnertorquecalc.html
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php
http://www.superchevy.com/how-to/en...-0902-chevy-engine-port-variations-measuring/
http://www.hotrod.com/articles/choosing-the-right-camshaft/
http://garage.grumpysperformance.com/index.php?threads/bits-of-383-info.38/
 
Last edited:
Hey Grumpy, I took your cross sectional data and put it into an Excel table. Then I made a JPG graphic file from it.

HeadsVsPortFlow.JPG
 
Thanks guys for the replies and the information. Grumpy, I see your cyl head list features the TFS twisted wedge first version. My heads are the second version. In fact I waited a year for these heads as TFS was in the process of development when I ordered them back in 1999. These are a little different, with valve angles of 16 degrees intake and 18 degrees exhaust. The intake ports were enlarged to 190cc, the valves to 2.02 and 1.6. They flowed 257 out of the box. I cleaned up the bowls, removing the seat ridge and smoothed the transitions out to the 1205 port entries. After the port work, they flowed right at 270. Pretty decent for 17 year old heads. I pushed the limits on cam selection. Using a dial indicator to measure valve to piston clearance, which came out to .120. In another year or two, when I'm ready to build a bigger cube SBC, I will have the valves and guides refreshed and may revisit the ports with what I've learned since the original job.

I'm a little disappointed in the XT runner castings. It's such a great design. I wish they at least left enough material in the runners to allow for porting to suit a larger intake port. They will be thin by the time I take them out to the 1205 dimensions. I may end up having to get them welded up to have sufficient material. I'll measure with a caliper to see how they do as I open them up. There's plenty of room for cutting back the injector bosses where they protrude into the runners. I can smooth those out quite a bit.

I think the ZZX cam will work well with this intake and head combo. The single pattern favors a good flowing intake side. Since I already have it installed in the motor, I've got to give it a try.
 
the ZZX from TPIS. 239 int dur.239 ex dur. .559/ .559 lift .. 112 lsa
the cams power range will be in the 2800 rpm- to about the 6000 rpm range
and youll want about 10:1 plus compression,
Id point out that that cam will require... a manual transmission OR A 2800 rpm-3200 rpm stall speed converter on and auto transmission,
and a 3.54"1-3.73:1 rear gear, and most likely 38lb-42 lb fuel injectors to work at max efficiency.
given the correct matching components, and a good low restriction tuned exhaust.. well over 450 hp should be fairly easy to exceed

http://garage.grumpysperformance.com/index.php?threads/porting-can-help.462/page-3#post-59145

http://garage.grumpysperformance.com/index.php?threads/port-matching-procedure-step-by-step-guide-with-pictures.5378/#post-71848

http://garage.grumpysperformance.com/index.php?threads/my-current-corvettes-383-combo.430/
 
Last edited:
Thanks Grumpy. I'm pretty close to your recommendations. I will try to get started on this intake in the next month so I can post some progress photos.
 
Thanks Grumpy.

I just did some more reading of the information you posted for me. I see you are familiar with the TFS G2 heads. As you say, there are better options available today than when the G2s we're released. Not too many though that outperform the G2s by very much. Especially in terms of flow vs runner volume. Looking at your photos of the terrible intake valve pocket in its as cast form, and it still flowed 257cfm. It's not hard to imagine 300cfm with that mess cleaned up.

I still feel like the reason TFS stopped making the twisted wedge for chevy was a broad misunderstanding of cam selection with the canted valves. As evidenced by my use of the ZZX, the G2s will fit a good sized cam. Just have to be careful with LSA and check clearance.

I didn't measure minimum csa when I finished porting the heads before assembly 17 years ago. I had one head off 8 years ago but again didn't take the time. I would like to know where they ended up. A huge improvement certainly over as cast.
As far as porting the XT goes, I've pretty much settled on a mild clean up of the runner castings with a bit of detail at the exits and entries. I will give attention to the injector bosses that protrude more than they need to into the runners. All this can only help. Later, when I have more detailed info on the post csa and can make the calculations, I'll take another look at the intake. That will be in preparation for a larger motor.
 
Again, I'll post photos as soon as I can and update as I make progress. With the holidays in full swing and being busy at the shop, time is tight just like money is right now.
 
Here are some photos of the XT before any work is done to it.
 

Attachments

  • 20171121_095414.jpg
    20171121_095414.jpg
    38.4 KB · Views: 11
  • 20171121_095434(0).jpg
    20171121_095434(0).jpg
    31.2 KB · Views: 10
  • 20171121_095459.jpg
    20171121_095459.jpg
    44.2 KB · Views: 55
That's right Grumpy. This is the way it's shipped from Edelbrock. I will have the top of the plenum cut off to access the runner entries and so that I can finish the plenum interior. Once I'm done with the porting, I'll have the top welded back in place.

I don't have enough information to accurately calculate the ideal runner csa for my engine combo. Since I am not prepared at this time to get that involved in redesigning the intake, and I don't have enough info to accurately calculate the best csa anyway, I'm just going to do a minor cleanup and smoothing of the runners and plenum. I will improve its fit to the G2 meads and move the torque curve upward around 500 rpm which this 355 should like. I'll save any more involved work on the manifold until I've been back into the heads and have more information.

You're familiar with the twisted wedge G2s. I'm guessing your porting job is probably a lot more accurate than what I did 16 years ago on these heads of mine. I didn't measure csa after finishing the port work. I know that I did open up the pockets behind the valves flush with the seats. I kept the swirl vanes and I profiled the guide bosses. I also worked on the short side radius to produce the smoothest path I could without getting the walls too thin. I of course also worked the exhaust ports, especially the short side radius. As you said, the G2s have great exhaust flow already. That's why I chose the ZZX to fit these heads. I installed SLP 1 3/4" primary short tube headers to fit the heads and have dual 2 1/2" pipes.

If I could edit my previous post I would rewrite it to say that the single pattern cam favors the intake side, not a high flowing intake. If I do leave the XT runner a little on the small side, the ZZX will help cover some of this.
 
you appear to be doing everything that can reasonably done to improve flow on that basic EFI intake design.


as always theres options that are always a compromise in some areas,
especially if your a tool junky and own a mill and a few welders and are more concerned with function than visual appeal, and your willing to test and tune several designs
I decided to use my mill and welder to custom fabricate a basic stealth ram
once it was rather extensively ported it made decent power even if it did not look a aesthetically all that pleasing



hood clearance is an issue as several other factors
the holley stealth ram base can be modified
http://garage.grumpysperformance.com/index.php?threads/tuning-a-tunnel-ram-intake.5175/
ok here, I got my kid to take pics, this is how far the stock hood will close on a stock hood with the stealth ram installed
dsc_022.jpg

dsc_023xc.jpg

you can even custom fabricate a plenum to gain the required hood clearance too use a stealth ram base.
pictured below, is one of several of my custom fabricated plenums , I built and tested on a stealth ram base required to gain the required hood clearance

custom%20stealth%20ram%201a.bmp

portedhsr.jpg


http://www.jegs.com/webapp/wcs/stores/servlet/topcategory_10001_10002_-1

https://www.ebay.com/itm/Weiand-908...For-Use-With-144-174-Blower-Kits/400669303867


https://www.ebay.com/itm/Weiand-622...r-Small-Block-and-Big-Block-Chev/112273744933


6221.jpg


Have one to sell? Sell now
Weiand 6221 Offset Thermostat Housing Adapter For Small Block and Big Block Chev
your problem is VERY COMMON, if the throttle body and thermostat housing has a clearance issue on some modified EFI intakes, heres the usual cure


COMMON SBC INTAKE PORTS
felpro # 1204=Port Size: 1.23" x 1.99"=2.448 sq inches

felpro # 1205=Port Size: 1.28" x 2.09"=2.67 sq inches

felpro # 1206=Port Size: 1.34" x 2.21"=2.96 sq inches

felpro # 1207=Port Size: 1.38" x 2.28"=3.146 sq inches

felpro # 1209=Port Size: 1.38" x 2.38"=3.28 sq inches

felpro # 1255 VORTEC=Port Size: 1.08" x 2.16"-2.33 sq inches

felpro # 1263=Port Size: 1.31" x 2.02"=2.65 sq inches

felpro # 1266=Port Size: 1.34" x 2.21"=2.96 sq inches

felpro # 1284 LT1=Port Size: 1.25 x 2.04''=2.55 sq inches

felpro # 1289 FASTBURN=Port Size: 1.30" x 2.31" 3.00 sq inches

http://users.erols.com/srweiss/calccsa.htm
stealthram radius.jpg

stealthram base
stealthbased.jpg

trampic8.jpg


efitu2.jpg

related threads
theres a good deal of related info in the links


http://garage.grumpysperformance.co...rger-intake-runners-l98-tpi.13785/#post-70716

http://garage.grumpysperformance.com/index.php?threads/ideal-tpi-build.12203/#post-59272

http://garage.grumpysperformance.co...st-flow-ratio-and-cam-timing.9725/#post-56700

http://garage.grumpysperformance.co...8mm-throttle-body-on-your-tpi.290/#post-54181

http://garage.grumpysperformance.co...sure-hurting-your-combo.495/page-2#post-53630

http://garage.grumpysperformance.co...ther-efi-intake-manifold-info.431/#post-48733

http://garage.grumpysperformance.com/index.php?threads/a-well-designed-c4-exhaust.786/#post-46459

http://garage.grumpysperformance.com/index.php?threads/can-you-get-there-with-tpi.10494/#post-44299

http://garage.grumpysperformance.co...e-body-coolant-bypass-thing.10544/#post-44875

http://garage.grumpysperformance.co...ps-on-building-a-tpi-383-c4.10434/#post-43430

http://garage.grumpysperformance.com/index.php?threads/port-and-runner-math.148/#post-16494

http://garage.grumpysperformance.co...or-piston-dome-or-port-volume.2077/#post-9049

http://garage.grumpysperformance.co...e-stock-tpi-engine-components.1509/#post-3459
 
Last edited:
Thanks Grumpy. I like your work on the Stealth Ram. I thought about that as an option when I considered which intake to go with.

I think the XT will work well for me. With a little port cleanup, it will work well on my current 355 and the ported G2s with the ZZX cam. It will definitely be a big power gain over the TPI I've been running since 2000. This TPI is about max of what a TPI, short of the First big dog, can be. It is the Superram base, ported to its limit without welding, the TPIS large tube runners, and ported plenum with a 58mm throttle body. It runs pretty well but I just want more. Plus, adding the intake now is one more step in preparation for the next engine. One less part I have to buy. I was going to go ahead and prepare the XT as if it was going on a 383 or 406. Now that I know there is a lot more I can do to make that work its best, once I have the all the dimensions of the intake ports, I'll wait until then to go all out. For now, I'll just do my thing polishing up these runners and streamlining things. Then I'll put it all together and enjoy what should be a 60hp boost with a wider flatter torque curve.

The XT will take some serious work to make it what I want it to be when it goes on the bigger motor. That motor will be built to run higher revs safely with a stronger more stable bottom end. I'll have the G2s freshened up and revisit my port work with what I have learned in 17 years. Then armed with all the information, I'll figure out just what to do with the XT to make the most of these heads and a cam to go with them.
 
Sorry, no photos yet. No progress yet. I've been reading through the links Grumpy posted for me, studying up to prepare for this intake swap. One thing I came across was an article detailing an HSR install on an IROC. I was surprised to read that they had hood clearance issues. The interference occurred at the front of the throttle body. This gives me pause considering that the TB on the XT stands at least as tall as that of the HSR. A big part of the problem is the bulky 90mm TB Eddy designed the XT around and the fact that it protrudes above the top of the plenum. I'm seriously considering modifications to the XT to fit the 58mm dual TB that I already have on my TPI. Using this TB would save me a bit of additional work swapping cables and adapting TPS and IAC harnesses. More importantly, it would allow me to modify the TB mounting of the XT to provide ample hood clearance in the IROC.

One article that I've looked through a few times, covered installation of the XT on a C4 vette. They had only minimal clearance issues and were able to mildly modify the front corner of the manifold to achieve clearance. Having worked on a few C4s and being familiar with their slim hood profile, I was encouraged that the XT fits this car. Now, I'm having second thoughts. I'll get hold of some Playdo(maybe borrow some from the grandkids) and use it to do some measuring of hood clearance on my 87 IROC. If it looks like clearance may be an issue, I'll go to work figuring out how to adapt the 58mm TB. I see that there is one adapter available but I don't know how it might affect airflow into the plenum. I have no problem modifying the XT to make the 58mm TB work its best. I wish I had Grumpy's welding and milling capabilities. I would really go to town on this thing.

I'll keep you guys posted.
 
Here's a link to a thread on a Corvette forum where a member made his own adapter to install his dual blade TB on the XT. I had seen this thread before and passed it by, thinking I would use the 90mm TB from Eddy. Last night as I thought this over, I pretty much decided that I will adapt my 58mm TB to the XT. In fact, if done correctly, it may work better with the XT's plenum to provide balanced cylinder filling than the 90mm.

https://www.corvetteforum.com/forum...e-with-diy-adaptor-for-tpi-throttle-body.html


Here is another way to install the Pro Flo XT on a 350 C4 Vette. I made an adaptor so I could use my TPI TB and cables. I also reused my Holley SP fuel rails and regulator. You need a small HEI distributor and remote coil. I used a TPIS Mini ram water neck. With this setup, hood clearance is no problem, about a ½ inch at the TB. (See the photo with the yellow clay on top of the TB). I made the adapter with a 2in hole saw and a drill press. I cut off the upper tab for the LS TB with a circular saw and a plywood jig bolted to the manifold to cut straight. I drilled and tapped the side of the intake to mount a Holley throttle cable bracket to the driver’s side of the intake. I made a plastic wedge to get it to line up with the TB. I haven’t had it dynoed but my SOTPs meter feels good.


80-img_20140403_203022_445_715111e7b3792388a92540c0c8f9f2b7196b2af1.jpg

http://garage.grumpysperformance.com/index.php?attachments/20171121_095414-jpg.9011/

80-img_20140323_174408_625_b7ec2a746f9f486e909f82d0df08ecbe4bdca45d.jpg



80-img_20140323_174241_057_9ea80ff1623621f04f5e65d0457174945149a2b9.jpg



80-img_20140322_142418_856_337dcd12eaae3056d07e30564d8162b662bd4f54.jpg
 
Last edited by a moderator:
Back
Top